Closemouthed

Full definition of closemouthed

Adjective

1. reticent, secretive or uncommunicative
• 1852 James Fenimore Cooper - Home as foundAs much so as possible; they have hardly a way that you would like, my dear ma'am; and are as closemouthed as if they were afraid of committing themselves.
• 2001 C. R. Anderegg - Sierra Hotel: flying Air Force fighters in the decade after VietnamInstructors were notoriously closemouthed about their gunnery techniques.